U.S. Pat. No. 4,897,980, issued Feb. 6, 1990, discloses an apparatus for forming a bulk package, the bulk package including objects stacked in layers with each layer comprising a plurality of the objects disposed in rows, a bottom tray disposed under the lower-most layer, and a top cap positioned over the upper-most layer of stacked objects. The patent also suggests covering the bulk package with an outer wrap such as plastic film to protect the objects, which may, for example, be packs of paper towels, and contribute to the structural integrity of the bulk package.
In the commercialization of the bulk package disclosed in the U.S. Pat. No. 4,897,980, the practice has been developed of utilizing the Cobra Stretch Wrapper to wrap the bulk package which has been utilized in the field of paper products, namely, paper towel, paper tissue, and paper napkin products. In particular, the Cobra Stretch Wrapper (which is made available by MIMA PACKAGING, Boca Raton, Fla.) is currently employed to practice what is known in the art as the four-corner wrapping method with a heat-seal at the end of the wrap cycle. The four-corner wrapper with heat-seal process will be described in some detail below, but it may be summarized as a system which loops a plastic "rope" (formed by compressing a plastic web) about all four corners of both the bottom tray and top cap of the package. The mechanical action of guiding the plastic rope-like web segment over and under each of the corners results in a great deal of mechanical wear on the Cobra Stretch Wrapper, rendering it prone to mechanical failure.
Another aspect of the prior art four-corner wrapper with heat-seal process is that it employs the step of finishing off the wrapping operation by joining two terminal ends of segments of the web having a rope-like configuration by heat sealing. That is, two loose "rope" ends are compressed together between two heated metal pads to melt the ends in an attempt to bond them when cooling takes place.
While the heat-seal produced at the end of the wrap cycle has a pleasing aesthetic appear, it has been found that there has been an extremely high failure rate of the heat weld seals by the time the bulk package reaches its final destination. This will result in a long segment of plastic "rope" (which may be in the order of 10 feet or so) dangling from the bulk package. The dangling rope-like web segment is both unsightly and potentially hazardous since it can become entangled in fork-lift truck wheels and the like.
Another deficiency of the prior art four-corner wrapper with heat-seal process is that the equipment employed to heat bond the "rope" ends is quite complex and prone to "mechanical and electrical failure. Also, of course, wrapping about all four corners of the bottom tray and top cap uses a considerable amount of plastic web material.